1. Field of Invention
This invention relates to a progressively or continuously operative mold assembly, and particularly to a mold assembly operative to receive a material molten at a temperature in excess of 1700.degree.C in narrow recesses formed by mating mold elements traversing a mold filling station, and very quickly thereafter operative to discharge a fine crystalline abrasive material from spaced apart mold elements traversing a mold discharging station. Examples of such materials are fused alumina-zirconia or other fused abrasive oxide material, metal oxides or other non-metallic refractory material which melts at a temperature in excess of 1700.degree.C.
2. Description of Prior Art
U.S. Pat. No. 3,570,586 issued to Lauener on Mar. 16, 1971, describes and claims a caterpillar mold machine for casting strips of aluminum or an aluminum alloy between the ends of opposing runs of mold blocks shaped on their ends to form the requisite strip cross-section. Lauener is primarily concerned with very elaborate provisions for isolating the relatively high temperature portions of the blocks from the supporting low temperature portions of the blocks and the supporting and guiding structure for the blocks, in order to maintain within acceptable limits the distortion and deflection of the portions of the blocks at which the aluminum sheet is formed.
It is interesting to note that the elaborate precautions of Lauener to limit deflection and distortion of the mold blocks were incorporated in a machine designed to cast a metal molten at slightly more than 600.degree.C. In contrast, no such elaborate precautions are required in the high speed machine of the instant invention designed to cast materials molten in excess of 1700.degree.C.
U.S. Pat. No. 3,835,917 issued Sept. 17, 1974, to Gyongyos as a continuation of application Ser. No. 309,800 filed Nov. 27, 1972, now abandoned, also discloses a machine for the continuous casting of strips of non-ferrous metals such as aluminum and aluminum alloys evidently resembling the machine disclosed in U.S. Pat. No. 3,570,586 of Lauener. While Gyongyos makes no showing whatsoever of the manner in which the respective mold blocks are interconnected, there is a suggestion that they may be interconnected in a manner similar to that illustrated and described in Lauener Pat. No. 3,570,586.
Gyongyos contemplates a machine arrangement in which the run of blocks in which a sheet of aluminum is cast are disposed at from 3.degree. to 45.degree. from the horizontal with the consequent tendency that undesireable gaps tend to appear between adjoining mold blocks of the run along which the casting is formed. In order to prevent the development of such gaps, Gyongyos provides a pair of brake assemblies coupled to the opposite sides of a single block adjacent the lower end of the run of blocks with the intention that the brake assemblies be adjusted to sufficient resistance to prevent formation of gaps between any of the entire series of blocks above the break equipped block. This of course means that the drive means for rotating all of the blocks must be powerful enough to drive every block past the brake assemblies adjusted to withstand movement of the entire run of blocks tending to form gaps therebetween.
South African Patent No. 8975/72 granted Jan. 3, 1974, and entitled "Method of Producing Abrasive" describes and illustrates a batch type arrangement for forming relatively thin sheets of abrasive material in the spaces between a series of adjoining relatively thick metal plates dependent from a common supporting frame, first filling the spaces with molten abrasive material, and then allowing the abrasive material to cool and thereby form hardened thin sheets thereof, and thereafter shifting the plates manually within the supporting frame therefor to release the thin sheets of abrasive material from between the plates.
Theoretically, the contiguous pairs of relatively thick mold plates of the South African Patent referred to above positively limits the thickness of the relatively thin spaces therebetween, consequently accelerating the rate of chilling the molten abrasive material deposited therein, and thereby advantageously limiting the size of the crystals formed in each sheet of chilled abrasive material.
However, in order to produce a useful quantity of material apparatus constructed according to the South African patent is necessarily relatively large and heavy, since it contains a substantial number of thick metal mold plates between which thin sheets of an abrasive material are formed. To date, the operation of this equipment has been either manual or manually controlled. That is, after the mold is filled with molten abrasive material, it is set aside to cool after it is filled with a molten abrasive material in excess of 1700.degree.C, and then the thick metal plates are prided apart to free the hardened thin sheets of abrasive therebetween. The time involved in this manually controlled or manual operation is such that most of the sensible heat of the molten abrasive material in excess of 1700.degree.C is transferred during the operation to the thick metal plates with resultant permanent deformation thereof. Consequently, the thick metal plates in fact must be reworked or replaced at relatively frequent intervals at a substantial cost for such rework or replacement, in order to maintain an approximation of the proper thickness therebetween.
In contrast to the batch type apparatus described and illustrated in the South African patent referred to above, the present invention contemplates very rapidly traversing a single series of consecutive thick plates with thin spaces therebetween first sequentially through a mold filling station and then sequentially along suitable guide rails toward a mold discharging station, with adjacent plates held tightly together both at the mold filling station and along the guide rails, and then sequentially through a mold discharging station, with the adjacent plates held spaced apart, all in one rapid continuous operation.
By this means, the transfer of sensible heat to the plates and consequent deformation of the plates is held to a minimum, notwithstanding temperature of the molden material in excess of 1700.degree.C.
Incidentally, the present invention shares with the apparatus of the South African patents referred to above the ability to protect from the atmosphere almost the entire surface of the molten abrasive material while it cools, and the ability to limit positively the thickness and thereby control the physical properties of the thin sheets of material produced therein.